1. Field of the Invention
The present invention relates to a hinge device in an aquarium tank for raising tropical fish etc., particularly an aquarium tank comprising a tank body and a lid member mounted on the tank body and provided with an openable and closable front lid.
2. Description of the Prior Art
An aquarium tank good in appearance and having a filter device, an illuminator, etc. which are easy to mount is disclosed in U. K. Patent No. 2,239,402, for example. The prior art aquarium tank comprises a tank body and a lid member mounted on the tank body. The tank body comprises a main frame made of synthetic resin or the like and open on the front, portions of the opposite sides and top, and a transparent frame made of glass, synthetic resin or the like, having a U-shaped sectional profile and mounted in the main frame so that the open front and side portions of the main frame are closed watertightly. The lid member is made of synthetic resin in the form of a shallow dish, has an openable and closable front lid for use in feeding tropical fish etc. and a rear casing in which an illuminator etc. are stored, and is provided on the back surface thereof with a receptacle for a heater etc. The front lid has a pair of bosses projecting toward each other and inserted into shaft holes formed in the framework of the lid member and is thus pivotally attached to the framework of the lid member. In this simply constructed hinge device, where the bosses have a short length, they are liable to disengage from the shaft holes, allowing the front lid to detach from the framework of the lid member. Where the bosses have a large length, it is necessary to widen the distance between the bosses by deforming the front lid when the bosses are inserted into the shaft holes. Such large length of the bosses does not pose a serious problem if the aquarium tank is of a small size. In the case of a large-sized aquarium tank, however, the front lid is difficult to deform and, if the front lid should be made of a deformable material, a strength problem arises.
The front lid and the framework of the lid member can be pivotably attached by screwing from the outside. However, this method poses a problem of workability and detracts from the appearance of the aquarium tank.
The front lid can also be pivotably attached to the framework of the lid member by inserting a coil spring and a pin shaft into a bearing hole and fitting the pin shaft loosely in a shaft hole utilizing the biasing force of the coil spring. In this case, since the coil spring and pin shaft are separate parts, handling and assembly of these parts is troublesome. For example, there is a possibility of coil springs getting entangled with each other during storage and, in such a case, they must be detached before the assembling process. Since the coil springs are used in a highly moist environment and are liable to be wetted with water, they are required to be made of stainless steel or to be plated. This increases the cost of the parts.
The present invention has been proposed to solve the problems mentioned above and has as its main object to provide an inexpensive hinge device in an aquarium tank enabling a front lid to be easily attached to the framework of a lid member and efficiently operated, without detracting from the appearance of the aquarium tank.